New snubbered psu + amp verdict and pics

[Vikash]

After finishing the first channel I decided to have a listening comparisson of my new LM3886 NI amp and hi-cap snubbered PSU (courtsesy of Carlos), against my other LM3875 NI premium kit amp.

I'm convinced that there is a problem with my LM3875 implementation, but excuses aside I have found this new psu and amp combo to have some clear sonic improvements. And I mean clear.

This all began when comparing the LM3875 amp with a Proceed Amp 5 which is when the harsh top end and lack of bass in comparisson really stood out. Now there is much improved weight to the sound, and I could hear a huge improvement in the mid frequency seperation. (Hence why I need to relook at the LM3875 amp.)

There are still some inteference/grounding issues, but I feel this one will give the Proceed a run for its money.

Here's some pics:


Thought I'd have a little soldering exercise and went p2p to the extreme:


Finished amp section

[BWRX]

That sure looks like it was fun to solder! Nice job. Just be careful not to short anything out!

[carlosfm]

Originally posted by Vikash
...but I feel this one will give the Proceed a run for its money.

I expect that.
But... that p2p on the chip is a little over the top.
Too many parts to make p2p...

[nina]

How is the 2200UF on chip sound -- compare with 1500 or 1000UF?

[pinkmouse]

C'mon Vikash, I really can't let you get away with that!

You're comparing two completely different amps and construction methods here, so stating that just the change in the PSU makes the difference isn't really very rigorous, is it?

Anyway, go inverting, and then you will be giving the Proceed a proper test. I really must send you a couple of OPA548s...

[Vikash]

Stop putting words in my mouth Mr. I would never be so bold as to say it was just the PSU. As it happens I've always been a little sceptical of *my implementation* of the rev 1 LM3875 kit which is to say that it was my first amp ever and I'm sure it has more potential. I really should get round to comparing it with the other LM3875 kits I've built (and reducing the 120mv offset )

I was expecting more bottom end with the new PSU - which it delivered, but I wasn't expecting the clarity change in the midrange which tells me there is something fundamental adrift in my LM3785 implementation, although with so many differences it really could be any or many things.

The bottom line remains though, it sounds better. Which is all I'm after really

On another note, I've been using the TB W3-871S monitors and they easily highlight changes between the Proceed and both chip amps. Quite impressive.

Nina, without swapping caps on the same amp it would be impossible to make a fair comparisson (Pinkmouse grrrrr). So far the mids are far better on the 3886 amp with 2200uf. The 3875 has 1500uf. Read from that and the above what you will

[Vikash]

Originally posted by carlosfm
But... that p2p on the chip is a little over the top.
Too many parts to make p2p...

You're getting soft in your old age carlos I think it's a work of art. Plus all the caps could not be closer to the pins

[enzedone]

It is interesting to hear about the differences. I am thinking about building the lm4780 next, but am still unsure if it will give me a better sound. The 3875 was quite nice apart from the small lack of base, but having very base orientated speakers, hasn't really been a problem.
But I can't afford to buy one and then be dissapointed.
By the way, i really love the Perspex amp. It has given me some new ideas, and i like anything thats not grey or aluminium.

[dw1narso]

Hi endzone...

The 3875 was quite nice apart from the small lack of base, but having very base orientated speakers, hasn't really been a problem

have you try to "snubber" your LM3875 amp PSU?

After 6 months live happily with standard PS of Brian GT's LM3875 kit (second generation PCB), last night I try to "snubber" one side of the PS (I use dual mono configuration) and then compare one channel to the other...

The result is exactly what Vikash said... detail increased, separation between instrument is better, and the most important is the base... which improve a lot.... (I test using some music... on Jennifer Warnes "The Hunter" track, on the opening part... I never realise that there is a strong/heavy low string sounds (bowed double bass) ... but now I can hear it)

So... before investing on LM4780... try "snubber" your amp first...
It is considerably cheaper with the very obvious result... :-)

I will definitely "snubber" the other PSU channel...

REgards,
---
David

[enzedone]

David,
I have no room in my current power box, it has been built around the transformer. So it's quite small. Anyway, i built it for my mother, who wanted a new stereo. I also built a pair of speakers, so i'll do all that next time around.